﻿using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace OBUActivation
{
    public class CRC
    {
        /// <summary>
        /// CRCTAB 表
        /// </summary>
        private static ushort[] crctab = new ushort[256]{
            0x0000, 0x1189, 0x2312, 0x329b, 0x4624, 0x57ad, 0x6536, 0x74bf,
            0x8c48, 0x9dc1, 0xaf5a, 0xbed3, 0xca6c, 0xdbe5, 0xe97e, 0xf8f7,
            0x1081, 0x0108, 0x3393, 0x221a, 0x56a5, 0x472c, 0x75b7, 0x643e,
            0x9cc9, 0x8d40, 0xbfdb, 0xae52, 0xdaed, 0xcb64, 0xf9ff, 0xe876,
            0x2102, 0x308b, 0x0210, 0x1399, 0x6726, 0x76af, 0x4434, 0x55bd,
            0xad4a, 0xbcc3, 0x8e58, 0x9fd1, 0xeb6e, 0xfae7, 0xc87c, 0xd9f5,
            0x3183, 0x200a, 0x1291, 0x0318, 0x77a7, 0x662e, 0x54b5, 0x453c,
            0xbdcb, 0xac42, 0x9ed9, 0x8f50, 0xfbef, 0xea66, 0xd8fd, 0xc974,
            0x4204, 0x538d, 0x6116, 0x709f, 0x0420, 0x15a9, 0x2732, 0x36bb,
            0xce4c, 0xdfc5, 0xed5e, 0xfcd7, 0x8868, 0x99e1, 0xab7a, 0xbaf3,
            0x5285, 0x430c, 0x7197, 0x601e, 0x14a1, 0x0528, 0x37b3, 0x263a,
            0xdecd, 0xcf44, 0xfddf, 0xec56, 0x98e9, 0x8960, 0xbbfb, 0xaa72,
            0x6306, 0x728f, 0x4014, 0x519d, 0x2522, 0x34ab, 0x0630, 0x17b9,
            0xef4e, 0xfec7, 0xcc5c, 0xddd5, 0xa96a, 0xb8e3, 0x8a78, 0x9bf1,
            0x7387, 0x620e, 0x5095, 0x411c, 0x35a3, 0x242a, 0x16b1, 0x0738,
            0xffcf, 0xee46, 0xdcdd, 0xcd54, 0xb9eb, 0xa862, 0x9af9, 0x8b70,
            0x8408, 0x9581, 0xa71a, 0xb693, 0xc22c, 0xd3a5, 0xe13e, 0xf0b7,
            0x0840, 0x19c9, 0x2b52, 0x3adb, 0x4e64, 0x5fed, 0x6d76, 0x7cff,
            0x9489, 0x8500, 0xb79b, 0xa612, 0xd2ad, 0xc324, 0xf1bf, 0xe036,
            0x18c1, 0x0948, 0x3bd3, 0x2a5a, 0x5ee5, 0x4f6c, 0x7df7, 0x6c7e,
            0xa50a, 0xb483, 0x8618, 0x9791, 0xe32e, 0xf2a7, 0xc03c, 0xd1b5,
            0x2942, 0x38cb, 0x0a50, 0x1bd9, 0x6f66, 0x7eef, 0x4c74, 0x5dfd,
            0xb58b, 0xa402, 0x9699, 0x8710, 0xf3af, 0xe226, 0xd0bd, 0xc134,
            0x39c3, 0x284a, 0x1ad1, 0x0b58, 0x7fe7, 0x6e6e, 0x5cf5, 0x4d7c,
            0xc60c, 0xd785, 0xe51e, 0xf497, 0x8028, 0x91a1, 0xa33a, 0xb2b3,
            0x4a44, 0x5bcd, 0x6956, 0x78df, 0x0c60, 0x1de9, 0x2f72, 0x3efb,
            0xd68d, 0xc704, 0xf59f, 0xe416, 0x90a9, 0x8120, 0xb3bb, 0xa232,
            0x5ac5, 0x4b4c, 0x79d7, 0x685e, 0x1ce1, 0x0d68, 0x3ff3, 0x2e7a,
            0xe70e, 0xf687, 0xc41c, 0xd595, 0xa12a, 0xb0a3, 0x8238, 0x93b1,
            0x6b46, 0x7acf, 0x4854, 0x59dd, 0x2d62, 0x3ceb, 0x0e70, 0x1ff9,
            0xf78f, 0xe606, 0xd49d, 0xc514, 0xb1ab, 0xa022, 0x92b9, 0x8330,
            0x7bc7, 0x6a4e, 0x58d5, 0x495c, 0x3de3, 0x2c6a, 0x1ef1, 0x0f78
                    };
        /// <summary>
        /// CRC校验公式
        /// </summary>
        /// <param name="crc">CRC</param>
        /// <param name="cp">发送的数据序列</param>
        /// <returns>新CRC</returns>
        private static ushort xcrc(ushort crc, byte cp)
        {
            ushort t1 = 0, t2 = 0, t3 = 0, t4 = 0, t5 = 0, t6 = 0;
            t1 = (ushort)(crc >> 8);
            t2 = (ushort)(t1 & 0xff);
            t3 = (ushort)(cp & 0xff);
            t4 = (ushort)(crc << 8);
            t5 = (ushort)(t2 ^ t3);
            t6 = (ushort)(crctab[t5] ^ t4);
            return t6;
        }

        /// <summary>
        /// 添加CRC校验字
        /// </summary>
        /// <param name="bufin">信息串</param>
        /// <param name="n">不包括校验字的串总长度</param>
        public static void ConCRC(ref byte[] bufin, byte n)
        {
            ushort crc16 = 0xFFFF;
            byte i;
            //n个数据的CRC校验
            for (i = 0; i < n; i++)
            {
                crc16 = xcrc(crc16, bufin[i]);
            }
            bufin[i] = (byte)(crc16 >> 8);
            bufin[i + 1] = (byte)(crc16 & 0xff);
        }

        public static string ConCRCStr(string bufin, int n)
        {
            byte[] bIn = StrToHex(bufin.Trim().Replace(" ", ""));
            ushort crc16 = 0xFFFF;
            ushort crcTemp = 0x0000;
            //return (CRC >> 8) ^ CRCtbl[(CRC & 0xFF) ^ b]; 
            for (int i = 0; i < n; i++)
            {
                //crc16 = xcrc(crc16, bIn[i]);
                //crcTemp = (ushort)(crc16 >> 8);
                //crc16 <<= 8;
                //crc16^=crctab[crcTemp^bIn[i]];
                crc16 = (ushort)((crc16 >> 8) ^ crctab[(crc16 & 0xff) ^ bIn[i]]);

            }
            //crc16 = (ushort)~crc16;
            return crc16.ToString("X4");

        }

        /// <summary>
        /// CRC数据验证
        /// </summary>
        /// <param name="bufout">信息串</param>
        /// <param name="count">接收数据总长度</param>
        /// <returns>true:校验成功,false:校验失败</returns>
        public static bool DataCRC(byte[] bufout, byte count)
        {
            ushort crc16 = 0xFFFF;
            byte i;
            for (i = 0; i < (count - 2); i++)
                crc16 = xcrc(crc16, bufout[i]);
            if ((bufout[count - 2] == (byte)(crc16 >> 8)) && (bufout[count - 1] == (byte)(crc16 & 0xff)))
            {
                return true;
            }
            else
            {
                return false;
            }
        }

        /// <summary>
        /// 字符串转16进制
        /// </summary>
        /// <param name="str"></param>
        /// <returns></returns>
        public static byte[] StrToHex(string str)
        {
            int len = str.Length / 2;
            byte[] hex = new byte[len];
            for (int i = 0; i < len; i++)
            {
                hex[i] = Convert.ToByte("0x" + str.Substring(2 * i, 2), 16);
            }
            return hex;
        }

        /// <summary>
        /// 字节数组转16进制字符串
        /// </summary>
        /// <param name="bytes"></param>
        /// <returns></returns>
        public static string HexToStr(byte[] bytes, int pos, int len)
        {
            string returnStr = "";
            if (bytes != null)
            {
                for (int i = pos; i < len + pos; i++)
                {
                    returnStr += bytes[i].ToString("X2");
                }
            }
            return returnStr;
        }
    }
}
